Hurricanes not only pack high winds, but can also cause torrential rains that lead to flash flooding and abnormally high waves and storm surge. Known as "the triple threat," each of these alone can pose a serious threat to life and property. Taken together they are capable of inflicting a large loss of life and widespread destruction.

High waves and storm surge

According to Jim Weyman, director of the Central Pacific Hurricane Center in Honolulu, "the greatest loss of life associated with tropical cyclones worldwide is due to coastal inundation from storm surge and high waves." Large ocean swell ahead of the hurricane may reach island shores while the storm is several hundred miles away. As the hurricane nears the coastline, rapidly rising water levels from the wind-driven waves and storm surge will inundate coastal areas, erode beaches, and pound and undermine waterfront structures and roadways.

In 1992, Hurricane Iniki's high waves and storm surge devastated the south shore of Kauai to elevations over 20 feet above sea level. Weyman urged, "People living near the coast at low elevations need to leave before the high waves and storm surge arrives. Be sure to follow any evacuation instructions given by the civil defense authorities."

High winds

In Hawaii, mountainous terrain accelerates hurricane and tropical storm winds causing extremely high winds that can destroy buildings, structures, trees, vegetation and crops. Ridge tops and exposed locations downslope from the mountains are at greatest risk. Weyman cautioned, "Before the arrival of a hurricane, consider moving to a home or shelter located in an area less exposed to the wind. Remain indoors during the period of strongest winds since debris carried by the wind can become deadly missiles. Beware of the momentary calm that occurs with the passage of the hurricane's eye. Winds will increase rapidly from the opposite direction on the other side of the eye as the center of the hurricane moves forward."

Heavy rain and flash flooding

Heavy and prolonged rains can accompany all types of tropical cyclones including hurricanes, tropical storms, and tropical depressions. Even the weakest tropical depressions can bring torrential rains and flash flooding to the Hawaiian Islands. Weyman concluded, "If heavy rains are forecast for your area and you live near a flood prone river or stream, leave before the heavy rains begin. Listen to radio, TV, or NOAA Weather Radio for flash flood warnings and move to high ground if flooding is imminent or already occurring."